Lasers drive nano locomotive

November 17/24, 2004

A researcher from Texas A&M University
and Fudan University in China has designed a laser-powered molecular locomotive
that runs along a molecular track and can generate a pulling force ten
times greater than that of kinesin, a biological molecular motor.

This is enough force to break multiple hydrogen bonds, break apart
molecules held together by electric charge, and loosen molecules held
together by hydrophobic, or water-repelled, sticking.

The molecular locomotive could someday be used to automatically
deliver molecular building blocks with nanometer accuracy, according to
the researcher. The mechanism could also eventually be used for drug delivery,
he said. A nanometer is one millionth of a millimeter, or the span of
ten hydrogen atoms.

The locomotive design calls for a polymer molecule that expands
and contracts when exposed to a laser with heads at both ends that chemically
bind to anchors on the track. Laser light would trigger binding and unbinding.

A series of six laser pulses of different frequencies powers the
locomotive. The molecule begins contracted, with both ends attached to
the track. The first pulse detaches the front end, the second pulse expands
the molecule, the third attaches the front end to a new binding sites
further down the track, the fourth detaches the rear end, the fifth contracts
the molecule, and the sixth attaches the rear end to a new binding site.

The molecular locomotive would measure about four nanometers in
diameter, with each unit of the molecule two nanometers long in its contracted
state. It would be capable of moving a few microns per second, which is
comparable to its biological counterparts.

A working prototype of the motor could be made within five years,
and practical applications are possible within ten years, according to
the researcher. The work appeared in the September 15, 2004 issue of Physical
Review E.